The nutrient you didn’t know you needed, and how to eat more of it
Many people are unaware of resistant starch and its potential health benefits. This particular type of fiber is now understood to be one of the best for gut health, lowering blood sugar and cholesterol levels, reducing inflammation, lowering the risk of chronic diseases, and even aiding in weight management. Surprisingly, it’s found not only in typical health foods like pulses, nuts, seeds, and whole grains, but also in everyday foods such as white toast, cold potatoes, overnight oats, under-ripe bananas, and reheated white rice or pasta.
How Resistant Starch Works
Most starchy carbohydrates are digested in the small intestine. However, resistant starch differs—it “resists” digestion there and travels further along the digestive tract to the large intestine, where it’s broken down by beneficial gut microbes. “Once in the large intestine, resistant starch ferments,” explains Rhiannon Lambert, a registered nutritionist and author of The Fibre Formula. This fermentation process, and its ability to act as a prebiotic, provides numerous health advantages.
Potential Health Benefits
The breakdown of resistant starch by gut microbes produces short-chain fatty acids (SCFAs), such as butyrate, which have positive health effects. Lambert notes that these SCFAs nourish gut bacteria and reduce inflammation, potentially lowering the risk of conditions like heart disease and obesity. Research led by John Mathers, professor of human nutrition at Newcastle University, suggests resistant starch may reduce the risk of certain cancers. In a study, benefits were most pronounced for upper gastrointestinal cancers—including esophageal, gastric, biliary tract, and pancreatic cancers—reducing some by over 60 percent.
Metabolic Health and Weight Management
Resistant starch also supports metabolic health and can reduce hunger. It slows down the breakdown of carbohydrates into glucose, preventing the rapid blood sugar spikes associated with cakes, biscuits, or refined cereals. “The presence of this type of beneficial starch means sugars are released into the bloodstream more slowly,” Lambert says, adding that it promotes feelings of fullness and can improve insulin sensitivity, aiding in weight management and type 2 diabetes control.
Maximizing Resistant Starch Intake
Here are some ways to increase your intake of resistant starch:
Overnight Oats vs. Porridge
Oats naturally contain resistant starch, but preparation matters. Cooking oats with heat and water causes the starch granules to swell, making them more easily digested. Soaking oats overnight, however, preserves more of the resistant starch. “Cooked porridge is still a great source of fibre, but overnight oats retain slightly more resistant starch,” Lambert explains.
Bananas: Slightly Underripe is Best
Firm, green bananas contain a higher proportion of resistant starch. As bananas ripen and turn yellow, enzymes convert the starch into sugar. By the time a banana is fully ripe with brown spots, much of the resistant starch has been lost.
Cooling Potatoes and Pasta
Cooking and then cooling potatoes and pasta increases their resistant starch content. When cooked, starch granules absorb water and burst. Cooling them causes the starch molecules to realign into a structure that’s harder for digestive enzymes to break down. This process can reduce the glycaemic index of potatoes by up to 25 percent and rice by up to 20 percent.
Rice: Refrigerate for 24 Hours
White rice benefits from the cooling process. Scientists in Indonesia found that cooling rice for 24 hours after cooking significantly increased its resistant starch content. However, it’s crucial to cool rice quickly—within half an hour—and refrigerate it at 4C to prevent the growth of bacillus cereus spores, which can produce toxins. Cooked rice should not be left at room temperature for more than an hour.
Pulses: A Natural Source
Lentils, chickpeas, butter beans, and kidney beans are naturally rich in resistant starch. The starch is trapped within the plant cell walls, meaning they don’t rely on cooling to create it. Cooking and cooling pulses may slightly increase resistant starch, but the effect is less significant than with rice or potatoes. Fava beans contain the most, with 8-12g per 100g, though they aren’t commonly consumed in the UK.
Chickpea Pasta: A Boost for Fibre Intake
Chickpea pasta offers a combination of fibre, protein, and resistant starch. Research showed that refrigerating chickpea pasta for 24 hours and then reheating it roughly doubled its resistant starch content.
Freezing and Toasting Bread
Freezing bread increases its resistant starch content due to structural changes. Freezing, defrosting, and toasting white bread can reduce its glycaemic index by 30-40 percent compared to fresh bread. Toasting fresh bread also lowers the glycaemic index, but to a lesser extent.
Resistant Starch and Weight Loss
Resistant starch may aid in weight management by reducing calorie intake and stimulating appetite-suppressing hormones. A 2024 study in Nature Metabolism found that participants consuming a resistant starch supplement lost an average of 2.8kg over eight weeks, while those receiving a regular starch powder showed no weight change. The resistant starch group also experienced better blood sugar control and increased levels of gut bacteria linked to weight reduction.
Is Resistant Starch Right for Everyone?
There are no official guidelines for resistant starch intake. The recommendation is to aim for 30g of fibre daily, with resistant starch being one component. It’s best to introduce resistant starch-rich foods gradually to avoid bloating. Individuals with IBS symptoms should consult a dietician.
Frequently Asked Questions
What is the difference between resistant starch and regular starch?
Most starches are digested in the small intestine, but resistant starch resists digestion and reaches the large intestine, where it’s fermented by gut microbes.
Can reheating foods reduce their resistant starch content?
No, reheating foods that have been cooked and cooled can actually *increase* resistant starch through a process called “dual retrogradation.”
Are there any side effects to eating more resistant starch?
Some people may experience bloating or gas when increasing their intake of resistant starch, so it’s best to introduce it gradually.
Considering the potential benefits for gut health, metabolic function, and even cancer prevention, how might incorporating more resistant starch into your diet impact your overall well-being?